def method(k, nums_in):
    # 处理成差值
    nums_in.sort()
    nums = []
    for i in range(1, len(nums_in)):
        cha = nums_in[i] - nums_in[i-1]
        nums.append(cha)
    
    # 滑动窗口
    left = 0
    right = -1
    s = 0
    max_ans = 0
    while right < len(nums) - 1:
        right += 1
        s += nums[right]
        while s > k:
            s -= nums[left]
            left += 1
        ans = right - left + 1
        max_ans = max(ans, max_ans)
    
    out = (max_ans + 1) / len(nums_in)
    return out

_, k = [int(x) for x in input().split()]
nums = [int(x) for x in input().split()]
out = method(k, nums)
print(out)
